Web/API/RTCDataChannel/bufferedAmount

This is an experimental technologyCheck the Browser compatibility table carefully before using this in production.

The read-only RTCDataChannel property bufferedAmount returns the number of bytes of data currently queued to be sent over the data channel. The queue may build up as a result of calls to the send() method. This only includes data buffered by the user agent itself; it doesn't include any framing overhead or buffering done by the operating system or network hardware.

The user agent may implement the process of actually sending data in any way it chooses; this may be done periodically during the event loop or truly asynchronously. As messages are actually sent, this value is reduced accordingly.

Closing the data channel doesn't reset this count, even though the user agent purges the queued messages. However, even after closing the channel, attempts to send messages continue to add to the bufferedAmount value, even though the messages are neither sent nor buffered.

Whenever this value decreases to fall to or below the value specified in the bufferedAmountLowThreshold property, the user agent fires the bufferedamountlow event. This event may be used, for example, to implement code which queues more messages to be sent whenever there's room to buffer them.

Syntax

var amount = aDataChannel.bufferedAmount;

Value

The number of bytes of data currently queued to be sent over the data channel but have not yet been sent.

Example

The snippet below includes a function which changes the contents of a block with the ID "bufferSize" to a string indicating the number of bytes currently buffered on an RTCDataChannel.

var dc = peerConnection.createDataChannel("File Transfer");

/* ... */

function showBufferedAmount(channel) {
  let el = document.getElementbyId("bufferSize");

  el.innerHTML = channel.bufferedAmount + " bytes";
}

Specifications

Specification	Status	Comment
WebRTC 1.0: Real-time Communication Between BrowsersThe definition of 'RTCDataChannel.bufferedAmount' in that specification.	Candidate Recommendation	Initial specification.

Browser compatibility

Update compatibility data on GitHub

	Desktop						Mobile
	Chrome	Edge	Firefox	Internet Explorer	Opera	Safari	Android webview	Chrome for Android	Firefox for Android	Opera for Android	Safari on iOS	Samsung Internet
`bufferedAmount` Experimental'	Chrome Full support 56	Edge Full support ≤79	Firefox Full support 18	IE No support No	Opera Full support 43	Safari Full support Yes	WebView Android Full support 56	Chrome Android Full support 56	Firefox Android Full support 18	Opera Android Full support 43	Safari iOS No support No	Samsung Internet Android Full support 6.0

Legend

Full support: Full support
No support: No support
Experimental. Expect behavior to change in the future.': Experimental. Expect behavior to change in the future.